There is no exact method to get the absolute path of an image in Magento 2.0. However, you can get the desired URL by using a combination of methods.
Firstly, you need to get the image object using the product interface:
$image = $product->getImage();
Then, you need to get the image URL using the image object:
$imageUrl = $image->getUrl();
Now, you can get the original image URL by adding '/original/' to the image URL:
$originalImageUrl = $imageUrl . '/original/';
This should give you the original image URL.